Many materials deteriorate in the presence of oxygen and water. Such materials typically include various metals such as iron, which corrodes in contact with water and oxygen such as in cooling water, drilling muds, and the like; but also include many materials of organic nature used industrially or in foods.
Partially hydrolyzed polyacrylamides and copolymers of acrylamide and acrylic acid, and the alkali salts thereof, are polymeric viscosifiers useful as mobility reducing agents in secondary and tertiary oil recovery processes. However, oxygen usually present in the thickened aqueous fluids containing such viscosifiers tends to degrade the polymer resulting in loss of solution viscosity.
Various methods have been used to avoid the deteriorative effects of oxygen on structural materials in contact with water, including various coatings, corrosion inhibitors, reducing agents to react with the oxygen, stabilizers, and the like. However, all have shortcomings in regard to toxicity, reactivity, cost, and/or lack of long term effectiveness.
Canned food and beverage products, such as wines, beer, ciders, and other closed-container-stored foods, can deteriorate even in the container when oxygen is co-present, as evidenced by changes in color, odor, taste, flavor, or vitamin content, or can rusting. The oxidative degradation also can occur after the container is opened. Canned fruit juices such as apple cider, orange juice, and the like, are adversely affected by oxygen. Other products such as canned vegetables and canned milk can also suffer detrimental effects.
Degradation of foods or degradation of polymeric viscosifiers in oil field fluids due to oxygen is a problem which has engendered numerous solutions.
The oil field fluid for example, can be drilling fluids or muds used in drilling wells. Such drilling fluids include, for example, weighted muds, unweighted muds, and salt water muds, and further can comprise additives frequently added to these muds such as carboxyalkyl ethers such as carboxymethylcellulose and the like, polyglycosans, polyacrylamides, and the like. These latter additives frequently are susceptible to oxidative degradation in the presence of free oxygen. In addition, the drilling fluids usually are handled by equipment susceptible to oxidative degradation as a result of the presence of free oxygen in the aqueous drilling fluid.
The term oil field fluid further includes such as workover fluids, which are aqueous fluids used after the well casing is set and usually, but not necessarily, after primary or self-pressurized recovery of hydrocarbon is terminated. As thus used, workover fluids include such fluids as water or brine floods used in secondary recovery as well as caustic flooding, steam, surfactant flooding and the like used in tertiary recovery. The term also includes mobility buffer fluids such as viscosified or thickened water wherein the water is viscosified or thickened by the addition of such as, for example, polyacrylamide, carboxyalkyl cellulose ethers, biopolysaccharides, and the like. Carbon dioxide which can be pumped into formations to reduce the viscosity of the hydrocarbon in situ for enhanced oil recovery can be present.
Frequently the presence of oxygen in these fluids is deleterious to one or more components of the fluid, i.e., one or more components of the fluid is susceptible to oxidative degradation or the presence of oxygen can be otherwise deleterious.
Thus, for example, polyacrylamides are known to degrade to smaller molecular fragments in the presence of free oxygen. Similarly, carboxyalkyl ethers of cellulose and polyglycosans or biopolysaccharides can be adversely affected by the presence of oxygen either directly or as mediated by aerobic microorganisms. Further small amounts of oxygen present in such as carbon dioxide used in enhanced oil recovery can greatly reduce solubility of the CO.sub.2 in the hydrocarbon in situ and thereby reduce the effectiveness of the CO.sub.2 for enhanced oil recovery.
In addition to these deleterious effects of oxygen on components of or the effectiveness of oil field fluids themselves, the presence of oxygen can be highly deleterious to the equipments used in handling such fluids such as, for example, pumps, conduits, well casings and the like.
The fluid comprising water and oxygen to be treated can be recycle water such as cooling water, and the like. The presence of free oxygen in such fluids can contribute significantly to the corrosion of associated equipments such as reservoirs, pumps conduits and the like.
New solutions to old problems are desirable, especially new ways which offer a significant advantage or improvement over previous methods.